Display control device and method

ABSTRACT

The present invention provides a device and a method for displaying appropriately on the display area for each processing unit such as an application according to the applied equipment. The CPU  12  processes display area acquisition requests from a plurality of processing units R 1 -Rn according to a display management program. The display management program decides whether use of the display area is allowed to each processing unit, considering the relationship of the plurality of display areas requested from each processing unit R 1 -Rn. Each processing unit R 1 -Rn executes display processing for the display area for which use is allowed. In this way, whether use is allowed is notified from the display management program to each processing unit R 1 -Rn after each processing unit R 1 -Rn sends the display area acquisition request. As a consequence, display in a plurality of areas by each processing unit R 1 -Rn can be controlled appropriately.

This application is a division of U.S. patent application Ser. No.09/320,543, filed May 27, 1999 now U.S. Pat. No. 6,710,789.

CROSS REFERENCE TO RELATED APPLICATIONS

All the disclosure in Japanese Patent Applications HEI 10-147815“Display control device and method” (filed on May 28, 1998) and HEI11-133419 “Display control device and method” (filed on May 14, 1999),including specifications, claims, drawings and abstract, are herebyincorporated herein reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technology for control display on ascreen by a plurality of processing units (tasks and applications), andmore particularly to an allocation of the display area.

2. Description of the Related Art

When a plurality of applications display on one screen, a window system,such as X-Window System, has been used. In these window systems, eachapplication displays acquiring the respective window (multi-window).

Japanese Laid-Open Patent Application HEI4-274289 discloses a devicewhich groups windows acquired by each application, and displays or doesnot display in group units.

Also in accordance with Japanese Patent Laid-Open No. 1-100662, whencontents displayed on a plurality of windows are inter-related, theseplurality of windows are simultaneously displayed so that the user caneasily understand the display contents.

However, with the conventional display based on a multi-window, whatapplication displays on what display area basically depends on theapplication. Therefore it is possible for an application to display awindow which overlaps with the window displayed by another application.When such a problem occurs, the user must change the position of thewindow which is overlapped by another window in order to view thedisplay of the window, which is troublesome.

In satellite broadcasting TV, where users need not change the positionsof windows, different applications must be used to prevent theoverlapping display of windows. For such devices, a conventional windowsystem cannot be used.

In accordance with the Japanese Laid-Open Patent ApplicationHEI4-274289, multiple windows specified by an application are grouped soas to improve the operability of each window, but the handling ofoverlapping of windows depends on the application. In other words, anundesired display of multi-windows is inevitable, and the abovementioned problems are not solved.

In accordance with the Japanese Laid-Open Patent ApplicationHEI1-100662, the handling of overlapping windows also depends on theapplication, where an undesired display of multi-windows is stillinevitable, and the above mentioned problems are not solved.

SUMMARY OF THE INVENTION

With the foregoing in view, it is an object of the present invention toprovide a device and a method which can display data in an appropriatedisplay area for each processing unit, such as an application, accordingto the applied equipment.

(1) A display control device and method according to the presentinvention defines a plurality of display areas in the display device,and when a display area acquisition request is received from eachprocessing unit, it is decided whether to use the requested displayarea, and the processing unit which is allowed to use the display areacan display data there. By defining display areas in advance, and byallowing the use of each display area, without leaving control to eachprocessing unit, an appropriate display for each processing unitaccording to the applied equipment becomes possible. Also inappropriatedisplay is prevented.

(2) When display area acquisition requests are received from a pluralityof processing units, the display control device according to the presentinvention judges whether the display areas subject to respectiveacquisition requests can coexist, and if the plurality of processingunits are requesting acquisition of display areas which cannot coexist,use is allowed to one of the processing units. As a consequence, aplurality of display processing which cannot coexist can be preventedand appropriate display becomes possible.

(3) When the display areas subject to respective acquisition requestsall or partially overlap, the display control device according to thepresent invention judges as coexistence impossible. As a consequence, itis possible to control such that displays by a plurality of processingunits do not overlap.

(4) When a plurality of processing units request acquisition of onedisplay area, the display control device according to the presentinvention judges as coexistence impossible. As a consequence, it ispossible to control such that two or more processing units are notallowed to use one display area.

(5) When a plurality of display areas subject to respective acquisitionrequests partially overlap, the display control device according to thepresent invention judges as coexistence possible. As a consequence, itis possible to control such that a partial overlapping display isallowed.

(6) When a display processing is executed for a plurality of displayareas which can coexist with partial overlapping portions, the displaycontrol device in accordance with the present invention displaysassigning priority to an area having a higher priority in the overlappedportion. As a consequence, it is possible to control such that theoverlapped portion is displayed according to priority.

(7) The display control device in accordance with the present inventionjudges the possibility of coexistence based on the coexistencerelationship information where the possibility of coexistence of aplurality of display areas has been defined in advance. As aconsequence, it is possible to quickly judge whether the requesteddisplay areas can coexist.

(8) When an acquisition request for a display area which cannot coexistis received, the display control device in accordance with the presentinvention allows use to the processing unit which sent the requestfirst. As a consequence, it is possible to assign priority to thedisplay by the processing unit which sent the display request first.

(9) When an acquisition request for a display area which cannot coexistis received, the display control device in accordance with the presentinvention allows use to the processing unit which has the higherpriority. As a consequence, it is possible to display data which is mosturgent, such as a warning display.

(10) When an acquisition request for a display area which cannot coexistis received, the display control device in accordance with the presentinvention allows use to the processing unit which requests the areahaving the highest priority. As a consequence, areas in a display can bedifferent depending on the urgency.

(11)–(14) The display control device according to the present inventionstores a processing unit which requested acquisition but was not alloweduse of the display area as an acquisition waiting, and allows use of thedisplay area when allowance is possible. As a consequence, use isallowed sequentially for display area acquisition requests. Eachprocessing unit does not have to request acquisition again. If use isallowed considering the order of received requests, priority given tothe processing units, and priority given to the display areas, then usecan be allowed according to sequence in the order considering suchpriorities.

(15) When a request for a display area which cannot coexist is received,the display control device according to the present invention changesthe display area requested by one or more processing units so as toallow use as a plurality of display areas which can coexist. As aconsequence, a plurality of displays can coexist as much as possiblewhile maintaining an appropriate display by a plurality of displayareas.

(16) When a request for a display area which cannot coexist is received,the display control device according to the present invention changesthe display area based on dependency relationship information definingthe changes of the display area to make coexistence possible. As aconsequence, the display area can be quickly changed so as to makecoexistence possible.

(17) (21) The display control device according to the present inventiondefines the processing units which are allowed use for each display areaas acquisition right information, and when a display area acquisitionrequest is received from each processing unit, the display controldevice refers to the acquisition right information and decides whetheruse of the display area is allowed for each processing unit. As aconsequence, it is possible to control by allocating processing unitsfor each display area.

(18) The display control device according to the present invention doesnot allow two or more processing units simultaneous use of one displayarea. As a consequence, it is possible to control so as to correlate adisplay area and a processing unit on a one-to-one basis.

(19) (20) The display control device according to the present inventionallows two or more processing units simultaneous use of one displayarea. As a consequence, it is possible to control so as to allow two ormore processing units to use one display area.

(22) (23) When the processing unit which requested the display area isactually not in a state to display on the display area, or is not in astate to execute processing related to the display processing, thedisplay control device according to the present invention does not allowthe processing unit to use the display area even if the display arearequested by the processing unit can coexist with display areasrequested by other processing units. As a consequence, to make displayefficient, use is not allowed for a processing unit which cannotactually execute display processing and processing related to display.

(24) The display control device according to the present invention alsohas display processing supervisory means, wherein when each processingunit executes display processing for each display area, it is supervisedwhether the display processing is by a processing unit which is alloweduse of the display area. As a consequence, execution of invalid displayprocessing can be supervised.

(25) (26) The display control device according to the present inventionassigns a key to the processing unit when use of a display area isallowed, and the display processing supervisory means supervises byjudging whether the key shown by the processing unit is the correct key.As a consequence, invalid display processing can be easily supervised.By assigning a different key each time, invalid display processing usingan old key can be prevented.

(27) When a processing unit attempted to execute display processing fora display area which is not allowed use is discovered, the displaycontrol device according to the present invention executes processing todisable the display processing by the processing unit. As a consequence,a processing unit which attempted invalid display processing can beremoved.

In the present invention, “processing unit” refers to a set ofprocessings to obtain a certain result. One processing unit may becomprised of one task, but may include two or more tasks.

The concept “case when all the display areas subject to the acquisitionrequests overlap” includes the case when two or more acquisitionrequests are received for the same display area.

“Cannot coexist” is the case when displaying in a plurality of displayareas is not desirable. Depending on the equipment to which the displaycontrol device is applied to or depending on the status, a plurality ofdisplay areas may not be able to coexist if a part of the display areaoverlaps, or may be able to coexist even if overlapping exists in apredetermined allowable range. There is also a case when a specificdisplay area can coexist even if it overlaps with another display area.

The concept “resource used by a processing unit” includes not onlyhardware but also software, such as data and programs.

The concept “display area storage means” refers to a means for storingthe definitions of display areas, and includes means for substantiallydefining display areas, regardless table format or descriptions in aprogram. In the embodiments, the display area definition table in FIG. 6falls under this concept.

The concept “display area management means” refers to a means fordeciding whether use of the area is allowed at least when a display areaacquisition request is received. In the embodiments, the display controlprogram shown in e.g. FIG. 8 falls under this concept.

The concept “computer” refers to a device which executes processingaccording to a program, and includes a personal computer, and a CPU andMPU built-in to such equipment as a TV.

“Recording medium where a program is recorded” is such a recordingmedium as ROM, RAM, a flexible disk, CD-ROM, memory card and hard disk,where a program is recorded. This concept includes not only such arecording medium as a hard disk which is connected to a CPU and withwhich the recorded program is directly executed, but also such arecording medium as CD-ROM which records a program to be executed afterinstalling it on a hard disk. A program here includes not only a programwhich can be directly executed, but also a source format program,compressed program and enciphered program.

Features, other objectives, applications and effects of the presentinvention will be clarified by referring to the embodiments anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing depicting an embodiment of a display control devicein accordance with the basic concept of the present invention;

FIG. 2 is a drawing depicting a general configuration of the displaycontrol device 2 according to the first embodiment;

FIG. 3 is a drawing depicting a hardware configuration when the displaycontrol device in FIG. 2 is applied to a digital broadcasting receiver;

FIG. 4 is a drawing depicting details of an AV decoder;

FIG. 5 is a drawing depicting an example of defining a display area;

FIG. 6 is a drawing showing content of a display area definition table;

FIG. 7 is a drawing showing content of an acquisition status storagetable;

FIG. 8 is a flow chart showing an acquisition request processing portionof a display control program in accordance with the first embodiment;

FIG. 9 is an example of a screen display on TV set 36;

FIG. 10 is an example of a screen display by a plurality ofapplications;

FIG. 11 is a flow chart showing a release request processing portion ofthe display control program in accordance with the first embodiment;

FIG. 12 is a drawing depicting a basic hardware configuration of thedisplay control device according to the embodiment of the presentinvention;

FIG. 13 is a drawing depicting a general configuration of the displaycontrol device 2 according to the second embodiment;

FIG. 14 is a drawing depicting a display area definition example;

FIG. 15 is a drawing showing content of a display area definition table;

FIG. 16 is a drawing showing content of an acquisition status storagetable;

FIG. 17 is a drawing showing content of a coexistence relationshiptable;

FIG. 18 is a flow chart showing an acquisition request processingportion of a display control program in accordance with the secondembodiment;

FIG. 19 is an example of a display of a program schedule on screen;

FIG. 20 is a flow chart showing a supervisory processing portion of thedisplay control program in accordance with the second embodiment;

FIG. 21 is an example of a display of a program schedule and weatherforecast;

FIG. 22 is a flow chart showing a supervisory processing portion of thedisplay control program in accordance with the second embodiment;

FIG. 23 is a drawing showing content of a display area priority table;

FIG. 24 is a flow chart showing an acquisition request processingportion of a display control program in accordance with the thirdembodiment;

FIG. 25 is a display area definition example on a screen;

FIG. 26 is a drawing showing a coexistence relationship table;

FIG. 27 is a drawing showing a display area priority table;

FIG. 28 is a flow chart of a program for display processing;

FIG. 29 is a drawing depicting an example of a screen when a displayarea for urgent display having high priority is created;

FIG. 30 is a drawing showing content of a processing unit prioritytable;

FIG. 31 is a flow chart showing an acquisition request processing of adisplay control program in accordance with the fourth embodiment;

FIG. 32 is a drawing depicting a general configuration of the displaycontrol device 2 according to the fifth embodiment;

FIG. 33 is a drawing showing content of a dependency relationship table;

FIG. 34 is a flow chart showing an acquisition request processingportion of a display control program in accordance with the fifthembodiment;

FIG. 35 is a drawing showing content of an acquisition status storagetable;

FIG. 36 is a drawing depicting a general configuration of the displaycontrol device 2 according to the sixth embodiment;

FIG. 37 is a drawing showing content of an available resource table;

FIG. 38 is a drawing showing content of a use resource table;

FIG. 39 is a flow chart showing an acquisition request processingportion of a display control program in accordance with the sixthembodiment;

FIG. 40 is an example of a display on a screen;

FIG. 41 is a flow chart showing an acquisition request processingportion of a display control program in accordance with the seventhembodiment;

FIG. 42 is a flow chart showing a release request processing portion ofthe display control program in accordance with the seventh embodiment;

FIG. 43 is a drawing showing an example of content stored in anacquisition waiting table;

FIG. 44 is a flow chart showing a portion of a processing acquisitionrequest in waiting status of the display control program in accordancewith the seventh embodiment;

FIG. 45 is a drawing depicting a general configuration of a displaycontrol device according to the eighth embodiment;

FIG. 46 is an example of a display area definition example;

FIG. 47 is a drawing showing a display area definition table;

FIG. 48 is a drawing showing an acquisition right information table;

FIG. 49 is a flow chart showing an acquisition request processingportion of a display control program in accordance with the eighthembodiment;

FIG. 50 is a drawing showing an acquisition right information table;

FIG. 51 is a drawing showing an acquisition right information tablewhere the upper limit of the number of usable tasks is limited;

FIG. 52 is a flow chart showing an acquisition request processingportion of the display control program; and

FIG. 53 is a drawing showing an acquisition status storage table.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Table of Contents

1. Display Control Device in Accordance with the Basic Concept of theInvention

2. First Embodiment

2.1 General Configuration

2.2 Example of Application to Digital Broadcasting Receiver

3. Second Embodiment

3.1 General Configuration

3.2 Embodiment Applied to a Digital Broadcasting Receiver

3.3 Handling of Task Attempted Invalid Processing

4. Third Embodiment

4.1 Example when Overlapped Areas are not Allowed to Coexist

4.2 Example when Overlapped Areas are Allowed to Coexist

5. Fourth Embodiment

6. Fifth Embodiment

7. Sixth Embodiment

8. Seventh Embodiment

9. Other Embodiments

10. Eighth Embodiments

10.1 General Configuration

10.2 Example when One Processing Unit is Allocated to One Display Area

10.3 Example when a Plurality of Processing Units are Allocated to OneDisplay Area

10.4 Example when a Plurality of Tasks are Allowed to Use One DisplayArea

1. Display Control Device in Accordance with the Basic Concept of theInvention

FIG. 1 shows a general configuration of the display control device 2 asan embodiment of the basic concept of the present invention. The displaycontrol device 2 comprises display area management means 4 and displayarea storage means 6. The display area storage means 6 storesdefinitions of a plurality of display areas which are set on a screen ofthe display device 8. To the display area management means 4, a displayarea acquisition request for displaying is sent from a plurality ofprocessing units R1-Rn. The display area management means 4 decideswhether use of the display area is allowed for each processing unit,considering the relationship of the plurality of display areas requestedfrom each processing unit R1-Rn. Each processing unit R1-Rn executesdisplay processing for the display areas for which use is allowed.

In this way, after each processing unit R1-Rn sends a display areaacquisition request, the display area management means 4 notifies eachprocessing unit R1-Rn whether use is allowed. As a consequence, displayon a plurality of areas by each processing unit R1-Rn can beappropriately controlled.

2. First Embodiment

2.1 General Configuration

FIG. 2 shows a general configuration of a display control device 2 as anembodiment of the present invention. In this embodiment, acquisitionstatus storage means 10 connected to the display area management means 4is disposed. The acquisition status storage means 10 stores theacquisition status correlating a display area and tasks T1-Tn which areprocessing units which acquired the display area. When a display areaacquisition request is received from one of the tasks T1-Tn, the displayarea management means 4 judges whether the display area has beenacquired by another task based on the storage content of the acquisitionstatus storage means 10. If the display area has been acquired byanother task, the task is not allowed to use the display area. If thedisplay area has not been acquired by another task, the task is allowedto use the display area.

2.2 Example of Application to Digital Broadcasting Receiver

FIG. 3 shows a hardware configuration when the display control deviceshown in FIG. 2 is applied to a digital broadcasting receiver. In thisexample, each function shown in FIG. 2 is implemented by CPU 12.

In satellite digital broadcasting and ground wave digital broadcasting,a plurality of services are multiplexed and sent as a transport stream.The radio wave captured by an antenna 38 is sent to a tuner 30. Thetuner 30 selects and demodulates the transport stream carrying thedesired service according to the control of the CPU 12. The demodulatedtransport stream is sent to a transport decoder (TS decoder) 32. Thetransport decoder 32 selects the desired service from the transportstream according to the control of the CPU 12, and outputs it to anaudio video decoder (AV decoder) 34. The AV decoder receives the data,decompresses the compressed data, carries out D/A conversion, andoutputs video composite signals (e.g. NTSC signals).

FIG. 4 shows details of the AV decoder 34. The decompression circuit 41decompresses the output from the TS decoder 32 and sends it to a videoRAM 42. In data broadcasting, display content is controlled byoverwriting the V-RAM 42 from the CPU 12. A composite signal generationcircuit 44 converts the content of the V-RAM 42 from digital to analogso as to convert to video composite signals.

Referring to FIG. 3, A TV set 36, which is a display device, receivesthe video composite signals and outputs images and sound. A modem 17,which is a communication control circuit, is used for communication withthe outside via telephone lines.

The CPU 12 controls the above mentioned receive processing according toa station selection application (program) recorded in a ROM 16. The CPU12 judges which service is to be received based on the input by theuser, which is input from an operation input section 40. The operationinput section 40 may be a receiving part of a remote controller (notillustrated) or operation buttons disposed on the receiver main body.

In the ROM 16, such tasks as a caption application, a program scheduleapplication, a program reservation application, a data receivingapplication, and a system setting application have been recorded, inaddition to the station selection application. Also in the ROM 16, adisplay control program and a display area definition table have beenrecorded. A work memory 14 functions as a work area of the CPU 12.

FIG. 5 shows a display area definition example on the screen of the TVset 36. In this embodiment, each display area E1–E3 is defined so as notto overlap with each other. In the ROM 16, a display area definitiontable (display area storage means) for indicating the definitions ofeach display area E1–E3 has been recorded, as FIG. 6 shows. In thisembodiment, the coordinates are indicated by display dots, where theupper left corner of the screen is (0, 0), the lateral direction is Xand the longitudinal direction is Y. The lower right corner is (679,339).

The work memory 14 has an acquisition status storage table for recordingacquisition status correlating each area E1–E3 and tasks which acquiredeach area, as FIG. 7A shows.

FIG. 8 shows a flow chart of an acquisition request processing portion(display area management means) of the display control program recordedin the ROM 16. Now, with reference to this flow chart, the case when adata receiving application (task T1) executes display processing for thedisplay area E2, will be described. The data receiving application is anapplication for receiving data broadcasting (e.g. weather forecastingdata) and executing display based on this data. At first the datareceiving application sends a request to acquire the display area E2 tothe CPU 12. The CPU 12 receives this request and starts the displaycontrol program shown in FIG. 8 (Step S201).

Then the CPU 12 reads the display task storage table in the work memory14, and acquires a use status of the requested display area E2 (StepS202). Based on the obtained status, the CPU 12 judges whether therequested display area E2 has been acquired by another application(task) (Step S203). Here, the display area E2 has not been acquired byany other task, as FIG. 7A shows. Therefore the processing advances toStep S204.

In Step S204, the data receiving application (task T1) is storedcorrelating to the display area E2 of the display task storage table.FIG. 7B shows the display task storage table after storing the task T1.

Then the CPU 12 notifies the data receiving application (task T1) toallow use of the requested display area E2. In this way, the datareceiving application (task 1) acquires a display right for the displayarea E2. The data receiving application which acquired the display areaE2 executes display processing for the area. In other words, accordingto the data receiving application, the CPU 12 overwrites the V-RAM 42based on the received content of the data broadcasting, and displaysdata broadcasting, as shown in FIG. 9.

A case when a program schedule application (task T3) requestsacquisition of the display area E2 again in the above status will beexplained. The program schedule application is an application to receiveand display an electronic program schedule (EPG). In this case as well,the display control program shown in FIG. 8 is started by theacquisition request from the program schedule application (task T3)(Step S201). The CPU 12 recognizes that the requested display area E2has already been acquired by the data receiving application (task 1)based on the acquisition status storage table (see FIG. 7B). Thereforethe processing advances from Step S203 to S207. In this embodiment, twotasks are not allowed to use the same display area, so the CPU 12notifies the program schedule application (task T3) that the displayarea E2 cannot be acquired (Step S207). The program schedule application(task T3) receives this message, and selects whether to wait until thedisplay area E2 is released or to request acquisition of another displayarea, or to give up display at this time.

FIG. 10 shows an example of the screen display when the program scheduleapplication requests to acquire a display area E3 and a programreservation application requests to acquire a display area E1 in theabove status. According to this embodiment, each application is alloweduse of a display area such that disorder is not caused by e.g.overlapping of a display by each application, therefore display by aplurality of applications can be appropriately executed, as shown inFIG. 10.

When the above data receiving application (task T1) which acquired thedisplay area E2 ends the display processing on the display area, thedata receiving application (task T1) requests release of the displayarea E2 to the CPU 12. FIG. 11 shows a flow chart of a processingprogram (release request processing) in this case. The CPU 12 receivesthe release request and starts processing shown in FIG. 11 (Step S301).At first, the CPU 12 obtains the working status of the display area E2,for which release was requested, from the acquisition status storagetable (Step S302). Since the content of the acquisition status storagetable at this point is as shown in FIG. 7B, the CPU 12 recognizes thatthe display area E2 has been acquired by the data receiving application(task T1).

Then the CPU 12 judges whether the task which requested the release hasactually acquired the display area. This judgment is made based onwhether the task which requested the release of the display area matchesthe task which has acquired the display area (step S303). This judgmentis made to prevent a task which has not acquired the display area fromrequesting an incorrect release. When the tasks do not match in StepS303, the display area is not released, and failure of the release isnotified to the task which requested the release (Step S307).

Since the data receiving application (task T1) which requested releaseof the display area E2 has actually acquired the display area E2 here,processing advances to Step S304. In Step S304, the task T1 which wasstored correlating to the display area E2 in the acquisition statusstorage table is deleted. As a result, the content of the acquisitionstatus storage table becomes the status shown in FIG. 7A. Therefore if anew acquisition request for the display area E2 is received, use can beallowed.

After deleting the task from the acquisition status storage table, theCPU 12 notifies the data receiving application (task T1) that the areais released (Step S305).

In the above embodiment, when display area acquisition requests arereceived from a plurality of applications (tasks), it is judged whetherthe display areas subject to the acquisition request are the same areas,and if they are, then the task which requested the acquisition first isallowed use of the display area. In other words, if a plurality of tasksrequest acquisition for the same display area, it is judged thatcoexistence is impossible, and if the tasks request acquisition fordifferent areas, then it is judged that coexistence is possible.

3. Second Embodiment

3.1 General Configuration

FIG. 13 shows a general configuration of a display control device 2according to the second embodiment of the present invention. In thisembodiment, coexistence relationship storage means 20 is disposed. Thecoexistence relationship storage means 20 stores the coexistencerelationship information to indicate whether a plurality of displayareas can coexist. The display area management means 4 judges whetherthe display areas desired by the acquisition requests from eachprocessing unit R1-Rn can coexist, based on the coexistence relationshipinformation of the coexistence relationship storage means 20. Ifcoexistence is impossible, the processing unit which requestedacquisition first is allowed use of the display area.

A display processing supervisory means 22 judges whether each displayprocessing by each processing unit R1-Rn is for a display area where useof each display processing is allowed. If the display processing is fora display area where use is not allowed, the display processing is notaccepted.

In the first embodiment, one task corresponds to one processing unit. Inthe second embodiment, however, the case where one processing unit R1includes a plurality of tasks T11-T1m will be explained. For example, aprogram schedule application as a processing unit includes three tasks,that is, 1) task 1, which sends operation input from an operation inputsection 40 to task 2 or task 3 depending on the situation, 2) task 2which displays the program schedule on screen, and 3), task 3 whichdisplays the details of the program on screen.

A display area acquisition request is sent from each processing unitR1-Rn, and use is allowed for each processing unit R1-Rn. An acquisitionrequest may be sent from each processing unit R1-Rn independently, or besent from a specific task of each processing unit R1-Rn as arepresentative of the processing unit. The latter case will be explainedbelow.

3.2 Embodiment Applied to a Digital Broadcasting Receiver

The case when the display control device 2 in FIG. 13 is applied to adigital broadcasting receiver will be explained. The hardwareconfiguration is the same as in FIG. 3. In the ROM 16, however,coexistence relationship information is also recorded, in addition todefinitions of the display areas and the display control program.

FIG. 14 shows the definitions of the display areas in this embodiment.In this embodiment, the display area E1 for the entire screen, thedisplay area E2 for the left half, the display area E3 for the righthalf, the display area E4 for the upper half, and the display area E5for the lower half are defined. This definition content is stored in theROM 16 as a display area definition table, as shown in FIG. 15. Also, asFIG. 16 shows, the work memory 14 stores the acquisition status storagetable which indicates the correspondence between a display area and theprocessing unit which acquires this area. In this embodiment, a keynumber is assigned to a processing unit which is allowed to display, asmentioned later. This key number is also stored in the acquisitionstatus storage table.

FIG. 17 shows the coexistence relationship table stored in the ROM 16.In this embodiment, areas cannot coexist if they overlap. In FIG. 17,display areas which cannot coexist are recorded for each display area,but display areas which can coexist may be recorded.

FIG. 18 shows a flow chart of the acquisition request processing portionof the display control program recorded in the ROM 16. Processing whenthe processing unit R2 requests acquisition of the display area E3 whilethe display area E2 has been acquired by the processing unit R1, asshown in FIG. 16B, will be explained. In this explanation, theprocessing unit R1 is assumed to be the program schedule application andthe processing unit R2 to be the data receiving application. In thiscase, the program schedule application, which is the processing unit R1,is currently executing display in the display area E2, as shown in FIG.19.

When the acquisition request is received from the task T21 (for example,a task for displaying the content of data broadcasting on screen), whichrepresents the data receiving application (processing unit R2), the CPU12 starts the processing shown in FIG. 18 (Step S401). Then the CPU 12refers to the acquisition status storage table, and obtains data onwhich processing unit has acquired each display area (Step S402). Inthis case, the display area E2 has been acquired by the program scheduleapplication (processing unit R1) and the other display areas are open.

Then referring to the coexistence relationship table in FIG. 17, the CPU12 obtains data on areas which cannot coexist with the display area E3requested by the data receiving application (processing unit R2) (StepS403). In this case, the display areas E1, E4 and E5 are the areas whichcannot coexist.

Then the CPU 12 judges whether the display area E3 for which acquisitionis requested has been acquired by another processing unit. Also the CPU12 judges whether one of the display areas E1, E4 and E5, which cannotcoexist with the requested display area E3, has been acquired by anotherprocessing unit. If one of these areas E3, E1, E4 and E5 has beenacquired by another processing unit, the CPU 12 returns an acquisitionfailure notice to the task which sent the request (Step S408).

In this case, all the display areas E3, E1, E4 and E5 are open, soprocessing advances to Step S405. In Step S405, the processing unit R2and the key number, corresponding to the display area E3, are stored inthe acquisition status storage table (see FIG. 16C). The CPU 12 sendsthe key number to the task T21 representing the data receivingapplication (processing unit R2) to notify that use of the display areais allowed (Step S406). The task T21 receives the key number andnotifies that the use of the display area E3 is allowed along with thekey number to the other tasks T22-T2 n (for example, a task fordisplaying the main menu, and a task for displaying the sub-menu)belonging to the data receiving application (processing unit R2). Inthis way, use of the display area E3 is allowed to the data receivingapplication (processing unit R2). In this embodiment, a key number,including date and time when use is allowed, is generated and assigned.In this case, the key number “3205151307” is generated as area number“3”, processing unit number “2”, month “05”, day “15”, hour “13” andminute “07”. The key number may be generated by another encryptionprocessing.

In this embodiment, it is supervised whether the display processinginstructions sent from each task belonging to each processing unit isfor the display area for which use is allowed. FIG. 20 shows a flowchart of the supervisory processing program (display processingsupervisory means). Supervision of display processing by the task T22belonging to the data receiving application (processing unit R2) whichobtained the display area E3 will be explained below.

The task T22 of the data receiving application notifies the requestingdisplay area E3, the assigned key number “3205151307” and the displaycontent (for example, “straight line, x1=10, y1=20, x2=10, y2=80”) tothe CPU 12. Receiving this, the CPU 12 starts the processing in FIG. 20(step S501). At first, the CPU 12 refers to the acquisition statusstorage table in Step S502, and recognizes that the key number of thedisplay area E3 is “3205151307” (see FIG. 16C). Then the CPU 12 judgeswhether the key number notified by the task T22 which requested displayprocessing and the key number of the acquisition status storage tablematch (Step S503).

When they do not match, the CPU 12 does not execute display processingregarding that the task belonging to a processing unit which is notallowed use of the display area attempts invalid display processing. Inother words, the display content is not displayed.

In this case, the key number “3205151307” matches, therefore the CPU 12judges the display processing request as valid, and executes the displayprocessing for the display area E3 (Step S504). As a result, the displaycontent is displayed. This display processing may be executed by the CPU12, or by another CPU or circuit.

In this way, the program schedule application uses the area E2 at theleft, and the data receiving application uses the area E3 at the right.If the program schedule application attempts display processing for thearea E3, or if the data receiving application attempts displayprocessing for the area E2, then the display processing is disabled bythe supervisory processing program. Thus the program is supervised so asto maintain an appropriate display by disabling display processing by atask belonging to a processing unit which is not allowed use of thedisplay area.

Next, the case when the caption application (processing unit R3)requests acquisition of the upper half display area E4 while the lefthalf display area E2 has been acquired by the program scheduleapplication (processing unit R1) (see FIG. 16B) will be explained.

When the acquisition request is received, the CPU starts the processingshown in FIG. 18 (Step S401). Since another processing unit has acquiredthe display area E2, which cannot coexist with the display area E4 inStep S404, the processing advances to Step S408. In Step S404, the CPU12 returns an acquisition failure notice to the processing unit R3. Inother words, in this embodiment, the left half display area E2 and theupper half display area E4 cannot coexist since they partially overlap.

In the above case, a key number is not assigned to a task belonging tothe processing unit R3, therefore display processing for the displayarea 4 cannot be executed. Even if display processing is attempted, thedisplay processing is disabled by the supervisory processing programshown in FIG. 20.

In this embodiment, a key number is encrypted by including such elementsas hour and minute. Therefore even when use of the same display area isallowed, the key number may be different for each assignment. In thecase of the status shown in FIG. 16C, for example, when the processingunit R1 releases the display area E2 and the processing unit R4 isallowed use of the display area, a key number different from the one forprocessing unit R1, that is, “2105151209”, is assigned. As aconsequence, even if a task belonging to the processing unit R1 attemptsdisplay processing for the display area E2 using the old key number,“2105151305”, the display processing is disabled.

3.3 Handling of Task Attempted Invalid Processing

In the above mentioned case, display processing by a task is notexecuted if key numbers do not match. However, as Step S506 in FIG. 22shows, subsequent processing may be completely disabled for theprocessing unit which requested the display processing. In other words,regarding the processing unit as a processing unit which attemptedinvalid processing, the display area which the processing unit hasacquired is forcibly released, resources the processing unit is usingare forcibly released, and information on the processing unit recordedin the kernel which is performing task control is deleted, so as toremove the processing unit. In this way, invalid processing by aninvalid processing unit can be prevented by removing the processing unitwhich attempted invalid processing.

4. Third Embodiment

4.1 Example when Overlapped Areas are Not Allowed to Coexist

In accordance with the above mentioned first embodiment and secondembodiment, when a plurality of processing units request acquisition ofdisplay areas which cannot coexist, the processing unit which sent anacquisition request first is allowed use of the display area. However,it is also acceptable that priority be assigned to each display area,and a processing unit which requested a display area which has thehighest priority among the plurality of processing units which requestedacquisition is allowed use of the display area.

An embodiment using this type processing will be explained below. Forconvenience of explanation, the second embodiment applied to a digitalbroadcasting receiver is basically used for explanation.

In the ROM 16 (FIG. 3), a display area priority table, as shown in FIG.23, has been recorded. The display area priority table defines priorityfor each display area. In this embodiment, the smaller the numberassigned as priority the higher the priority.

FIG. 24 shows a flow chart of the acquisition request processing portionof the display control program in accordance with the presentembodiment. The following explanation is based on the case when theprocessing unit R3 requests acquisition of the display area E1 (entirearea) while the processing unit R1 has acquired the display area E2(left half area), and the processing unit R2 has acquired the displayarea E3 (right half area), as shown in FIG. 16C.

When the acquisition request from the processing unit R3 is received,the CPU 12 starts the processing shown in FIG. 24 (Step S401). Thenreferring to the acquisition status storage table in FIG. 16C and thecoexistence relationship table in FIG. 17, the CPU 12 judges whether thedisplay area E1 requested by the processing unit R3 can coexist with theareas which have already been acquired (Steps S402, S403, S410). Sincethe display E1 cannot coexist with the display area E2 and the displayarea E3, the processing advances to Step S411.

In Step S411, referring to the display area priority table in FIG. 23,the CPU 12 judges whether the newly requested display area has a higherpriority than the display areas which have been acquired and cannotcoexist with the newly requested display area. If the priority is nothigher (priority is lower or the same), an acquisition failure notice issent to the processing unit which requested acquisition (Step S413).Since priority of the display area E1 requested by the processing unitR3 is “1”, and priority of the display areas E2 and E3 which have beenacquired is “2”, the display area E1 has the higher priority. Thereforeprocessing advances to Step S412.

In Step S412, the display areas E2 and E3 which have been acquired arereleased. In this case, the processing unit R1 and R2 are deleted fromthe display area storage table. Then processing advances to Steps S405and S406, and the processing unit R3 is allowed use of the display areaE1. As a result, use of the screen allowed to processing units R1 and R2is changed to use of the entire screen allowed to the processing unitR3.

In this way, in accordance with the present embodiment, when acquisitionof display areas which cannot coexist is requested, use is allowed to aprocessing unit which requested a display area having a higher priority.

4.2 Example when Overlapped Areas are Allowed to Coexist

In the above mentioned case, overlapped areas are not allowed tocoexist. However, overlapped areas may be allowed to coexist, where forthe overlapped portion, a display area having a higher priority isdisplayed with priority.

In this case, FIG. 25 shows the definition of the display areas, FIG. 26shows a coexistence relationship table, and FIG. 27 shows a display areapriority table. The flow chart of the acquisition request processing isthe same as FIG. 24.

Assume that an urgent display application requests acquisition of thetop part display area E4 while an application is using the display areaE1 on the entire screen. In this case, the urgent display application isallowed to use the display area E4 since the area E4 can coexist withthe area E1.

FIG. 28 shows a flow chart of the display processing program. It ispreferable to provide the display processing program as a part of theoperating system (OS). The case when an urgent display application whichis allowed to use the display area E4, as mentioned above, executesdisplay processing for the display area E4, will be explained as anexample. At first, the display processing request sent by the urgentdisplay application is judged whether it is a valid request by thesupervisory processing shown in FIG. 22. If judged as valid because keynumbers match, the display processing request is sent to the displayprocessing program of the OS in Step S504 in FIG. 22.

When the display processing request is received, CPU judges whether thetarget area of the display processing request (area E4 in this case)overlaps with another area for which use has been allowed (Step S801 inFIG. 28). Since it overlaps with the area E1 for which use has beenallowed here, processing advances to Step S802. In Step S802, CPU judgeswhether priority of the target area (E4 in this case) is higher thanthat of the other area (E1 in this case). Since the target area has thehigher priority here, processing advances to Step S803, and writeprocessing for the target area is executed. In other words, the CPU 12overwrites the target area (E4 in this case) portion of V-RAM 42according to the display processing request.

In this way, the urgent display, as shown in FIG. 29, is executed. Bycreating an area for the urgent display to overlap another area and byassigning a higher priority, as shown in this example, an appropriateurgent display becomes possible while efficiently using the screen.

When a display request processing is executed for the display area E1 inthe status shown in FIG. 29, the processing flow is as follows. Sincethe other area E4 has a higher priority in Step S802, processingadvances to Step S804. In Step S804, write processing is executed forthe target area, excluding the portion of the other area. In otherwords, the CPU 12 overwrites the target area E1 portion of V-RAM 42,excluding E4, according to the display processing request. As a result,the display area E1 can be overwritten without deleting the urgentdisplay of the display area E4.

5. Fourth Embodiment

In accordance with the third embodiment, when a plurality of processingunits request acquisition of display areas which cannot coexist, aprocessing unit which requested a display area having the highestpriority is allowed use of the display area. However, priority may beassigned to each processing unit so that a processing unit having thehighest priority is allowed use of the display area.

In this case, it is preferable that the processing unit priority tableshown in FIG. 30 is stored in the ROM 16, and the acquisition requestprocessing shown in FIG. 31 is executed. In FIG. 31, when a plurality ofprocessing units request acquisition of display areas which cannotcoexist, it is judged whether the processing unit newly requestedacquisition has a higher priority than a processing unit which hasacquired an area which cannot coexist (Step S414). If the processingunit which newly requested acquisition has a higher priority, thedisplay area of the processing unit which has acquired the display areais released, and the processing unit which newly requested acquisitionis allowed use of the display area (Step S412).

The order of acquisition requests, priority of the display areas, andpriority of the processing units may be freely combined in decidingwhich processing unit is allowed use of the display area.

6. Fifth Embodiment

FIG. 32 shows a general configuration of the display control device 2according to the fifth embodiment of the present invention. In thisembodiment, dependency relationship storage means 24 is disposed. In thedependency relationship storage means 24, display areas which cannotcoexist with the requested display area are indicated, and display areachange information for making display areas coexist has been recorded.Based on the information of the dependency relationship storage means24, the display area management means 4 judges whether a display areawhich cannot coexist with the requested display area have been acquiredby another processing unit. When the display area has already beenacquired, the display area management means 4 changes the alreadyacquired display area of the processing unit for making it coexist basedon the information of the dependency relationship storage means 24, andallows the processing unit which requested acquisition use of therequested display area.

The hardware configuration, when the display control device 2 in FIG. 32is applied to a digital broadcasting receiver, is the same as in FIG. 3.In the ROM 16, however, dependency relationship information is alsorecorded, in addition to the definitions of display areas and thedisplay control program.

The definitions of display areas in this embodiment are the same as FIG.14, and the content of the display area definition table is the same asFIG. 15. The acquisition status storage table is the same as FIG. 16.

FIG. 33 shows the content of the dependency relationship table forrecording dependency information. The dependency relationship table isstored in the ROM 16. The second line of this table, for example, showsthat when acquisition is requested for the display area E2, and if thedisplay area E1 has been acquired by another processing unit,coexistence is made possible by changing the area of another processingunit from E1 to E3.

FIG. 34 shows a flow chart of an acquisition request processing portionof the display control program recorded in the ROM 16. The case when theprocessing unit R2 requests acquisition of the display area E2 while thedisplay area E1 has been acquired by the processing unit R1 (see FIG.35A) will be explained below.

When an acquisition request is received from the processing unit R2, theCPU 12 starts the processing shown in FIG. 34 (Step S601). At first,referring to the acquisition status storage table, the CPU 12 judgeswhether the requested display area E2 has been acquired by anotherprocessing unit. If it has been acquired, processing advances to StepS611, and the CPU 12 returns an acquisition failure notice to theprocessing unit R2. In this case, the display area E2 is open, as shownin FIG. 35A, so the processing advances to Step S604.

In Step S604, referring to the dependency relationship table shown inFIG. 33, the CPU 12 obtains information on areas which the requesteddisplay area E2 depends on. In this case, the display areas E1, E4 andE5 are areas which the display area E2 depends on.

Then referring to the acquisition status storage table, the CPU 12judges whether the display areas E1, E4 and E5 which the display area E2depends on have been acquired by another processing unit (Step S606). Ifthey have not been acquired by another processing unit, the CPU 12allows the processing unit which requested acquisition to use thedisplay area in Steps S607 and S608, regarding that use of the displayarea will not cause any problems in terms of display area coexistence.In this case, the display area E1 (entire screen area) which the displayarea E2 depends on has been acquired by the processing unit R1.Therefore if use of the display area E2 (left half screen area) wereallowed to the processing unit R2, a part of the display area wouldoverlap and appropriate display would not be executed.

So in this embodiment, the display area of the processing unit R1 ischanged from E1 (entire screen area) to E3 (right half screen area)according to the dependency relationship table in FIG. 33 (Step S610).After this change, the processing unit R2 which requested acquisition isallowed use of the display area E2 (left half screen area). As aconsequence, the processing unit R1 displays on the right half of thescreen, and the processing unit R2 displays on the left half of thescreen.

In Steps S607 and S608, the CPU 12 releases the display area E1, and atthe same time notifies changes to the display area T3, a new key number,“3105151322”, to the processing unit R1, and sends key number“2205151321” to the processing unit R2 for the display area T2. FIG. 35Bshows the content of the acquisition status storage table after change.

In this way, when acquisition is requested for a display area whichcannot coexist, allocation of display areas is changed so thatcoexistence becomes possible.

In accordance with this embodiment, the display area which has beenacquired is changed to make coexistence possible, but the display areawhich acquisition is requested may be changed to make coexistencepossible. When the display area E2 (left half screen area) has beenacquired by the processing unit R1, for example, if the display area E1(entire screen area) is requested by the processing unit R2, the requestof the processing unit R2 may be changed to the display area E3 (righthalf screen area) for which use is allowed.

7. Sixth Embodiment

FIG. 36 shows a general configuration of the display control deviceaccording to the sixth embodiment of the present invention. In thisembodiment, an available resource storage means 28 and a use resourcestorage means 26 are disposed. The available resource storage means 28stores information on resources of each processing unit R1-Rn. Here theconcept “resource” includes not only such hardware as a modem, speaker,video equipment, CD-ROM and DVD drive, but also such software as dataand programs. The use resource storage means 26 stores the currentavailability status of each resource.

When a display area acquisition request is received from processingunits R1-Rn, the display area management means 4 judges whether thedisplay area can coexist with the display areas which have been acquiredby other processing units. If coexistence is not possible, theprocessing unit is not allowed use of the display area. If coexistenceis possible, the display area management means 4 obtains information ona resource to be used by the processing unit which requested acquisitionreferring to the available resource storage means 28. Then referring tothe use resource storage means 26, the display area management means 4checks whether the resource can be used now. If the resource cannot beused, the display area management means 4 does not allow the processingunit which requested acquisition use of the display area. This isbecause allowing use of the display area is meaningless since theprocessing unit cannot execute processing using the resource. Forexample, when the processing unit cannot display unless the resource isavailable, display is not executed even if use of the display area isallowed to the processing unit.

With the foregoing in view, it is preferable to judge whether resourcesrequired for display processing can be used. A resource which is notdirectly related to display processing but is very closely related toscreen display, such as a speaker, may also be judged whether it canactually be used. In other words, not only resources which theprocessing unit needs for display processing but also resources requiredfor sound processing related to the display processing may be judgedwhether they can actually be used.

The hardware configuration, when the display control device 2 in FIG. 36is applied to a digital broadcasting receiver, is the same as FIG. 3. Inthe ROM 16, however, the available resource table shown in FIG. 37 isstored. In the work memory 14, the use resource table shown in FIG. 38is stored.

FIG. 39 shows a flow chart of the acquisition request processing portionof the display control program recorded in the ROM 16. Here, the casewhen the task T2 of the processing unit R2 requests acquisition of thedisplay area E3 at the lower part of the screen while the task T1 of theprocessing unit R1 has acquired the display area E2 at the upper rightof the screen, as shown in FIG. 7B, will be explained. It is assumedthat the processing unit 2 is a browser application. The browserapplication accesses the Internet via a modem 17 to read home pages. Itis also assumed that the processing unit R1 is a telephone shoppingapplication which executes display, as shown in FIG. 40. Here, theviewer has selected a purchase application, therefore the CPU 12 callsthe reception center of the telephone shopping company via the modem 17.In other words, the modem 17 has already been used by the telephoneshopping application (processing unit R1) as shown in FIG. 38.

When an acquisition request is received from the browser application(processing unit R2), the CPU 12 starts the processing shown in FIG. 39(Step S701). Then referring to the acquisition status storage table inFIG. 7B, the CPU 12 judges whether the requested display area E3 hasbeen acquired by another processing unit (Steps S702, S703). In thiscase, the display area E3 is open, so processing advances to Step S704.

In Step S704, referring to the available resource table in FIG. 37, theCPU 12 extracts resources to be used by the processing unit R2 whichrequested acquisition. In this case, a modem and a speaker areextracted. Then referring to the use resource table in FIG. 38, the CPU12 judges whether the extracted modem and speaker are in use by anotherprocessing unit (Steps S705, S706). When all extracted resources can beused, the CPU 12 allows use of the display area to the processing unit,and writes that the resources to be used by the processing unit are inuse in the use resource table in FIG. 38 (Steps S708, S709).

In this case, the modem is in use by the telephone shopping application(processing unit R1), as shown in FIG. 38, so processing advances fromStep S706 to S710. In Step S710, the CPU 12 notifies the browserapplication (processing unit R2) that display area acquisition failed.In this way, it is judged whether use of the display area is allowedconsidering the use status of resources.

When a processing unit requests to release an area, the CPU 12 writesthe release of the resource which the processing unit has been using inthe use resource table. As a consequence, always the latest use statusis stored in the use resource table.

In accordance with the above embodiment, the resource cannot be used ifanother processing unit is using it. However, for a resource whichspecified the number of processing units (or tasks) that can be usedsimultaneously, whether that resource can be used may be judged by thenumber of processing units (tasks) which are actually using theresource.

In the above explanation, use of the display area is allowed afterjudging whether such a resource as a modem is available. However, whenthe processing unit is for displaying the data of an electronic programschedule, use of the display area may be allowed after judging whetherthe data is actually received. In other words, the resources include notonly hardware but also such software as data.

8. Seventh Embodiment

In accordance with the above embodiments, when acquisition is requestedfor a display area which cannot coexist, an acquisition failure noticeis returned to the processing unit. However, the processing unit whichis not allowed use of the display area may be stored as acquisitionwaiting, so as to acquire the display area when use can be allowed.

This embodiment will be explained based on the second embodiment in FIG.13. The flow chart of acquisition request processing is shown in FIG.41, instead of FIG. 18. The flow chart of release request processing isshown in FIG. 42. In the work memory 14, the acquisition waiting table,as shown in FIG. 43, is stored.

Here, the case when the content of the acquisition status storage tableis in the status shown in FIG. 16C (that is, the status when theprocessing unit R1 is using the left of the screen and the processingunit R2 is using the right of the screen) and the processing unit R4newly requests acquisition of the display area E2 will be explained. Itis assumed that nothing has been stored in the acquisition wait table,as shown in FIG. 43A.

When an acquisition request from the processing unit R4 is received, theCPU 12 refers to the acquisition status storage table (FIG. 16) andcoexistence relationship table (FIG. 17), and judges whether use of thedisplay area E2 can be allowed (Step S402, S403, S404). In this case,the display area E2 has been acquired by the processing unit R1 andcannot coexist, so processing advances to Step S410.

In Step S410, the CPU 12 notifies acquisition waiting to the processingunit R4, and the CPU 12 stores information that the processing unit R4is waiting for acquisition of the display area E2 in the acquisitionwait table (Step S411).

When processing units have already been stored in the acquisition waittable, the processing units may be rearranged according to predeterminedpriority. In other words, the processing units are rearranged such thata processing unit with a higher priority comes first. For the priorityused for this rearrangement, the order of sending acquisition requests,priority assigned to the requested display areas (see FIG. 23), andpriority assigned to processing units (FIG. 30), for example, can beused.

In this way, the processing unit which is not allowed use is stored inthe acquisition wait table.

Next, release request processing will be explained referring to FIG. 42.Here, it is assumed that the processing unit R1 requests the displayarea E2 in the status shown in FIG. 16C for explanation. The acquisitionwait table is assumed to be in the status shown in FIG. 43B.

When the release request is received, the CPU 12 refers to theacquisition status storage table, and judges whether the processing unitR1 which requested release of the display area E2 has acquired thedisplay area E2 (Steps S302, S303). Since the processing unit R1 hasacquired the display area E2 in this case, the CPU 12 deletes theprocessing unit R1 from the acquisition status storage table and returnsa release OK notice (Steps S304, S305).

Then the CPU 12 advances to Step S310 and reads the acquisition waittable, shown in FIG. 43B, from the beginning. Here, the request by theprocessing unit R4 for the display area E2 is read. For this acquisitionrequest in wait status, the CPU 12 executes processing of theacquisition request in wait status, as shown in FIG. 44. Since the areaE2 requested by the processing unit R4 can coexist in this case,processing advances from Step S404 to S405.

In Step S405, the CPU 12 stores the processing unit R4 in theacquisition status storage table and returns the key number to theprocessing unit R4 (Steps S405, S406). Then the CPU 12 deletes theacquisition request by the processing unit R4 for the display area E2from the acquisition wait table (Step S412).

In this way, the processing unit R4 can be allowed to acquire thedisplay area at the point when use of the display area becomes possible.

Then the CPU 12 reads the next acquisition request stored in theacquisition wait table, and executes the processing shown in FIG. 44 forthis request as well. This is because two or more requests may beallowed to use a respective area when the released area is large. Afterexecuting processing for all acquisition requests in wait status in theorder of priority, the CPU 12 ends release request processing (StepS407).

In accordance with this embodiment, each processing unit which requestedacquisition is eventually allowed use of the respective area accordingto the change of status even if use is not immediately allowed.

9. Other Embodiments

In the above embodiments, the case when the present invention is appliedto a digital broadcasting receiver was explained, but the presentinvention can be applied to equipment where a plurality of applicationsexecute display processing. In other words, the present invention can beapplied to equipment having the basic configuration shown in FIG. 12(the work memory 14 and the ROM 16 may be integrated). For example, thepresent invention can be applied to a home game machine, a telephonewith display and a personal computer.

In a car navigation system, the present invention can be applied fordisplaying map information and Internet information, for example.

Also in a DVD system, the present invention can be applied when imageinformation and such text information as a menu are displayed during theauthoring of images.

The present invention can also be applied to the screen display of apersonal computer. Particularly, the present invention is effective forcomputers used in factory automation (FA), where the user cannot changethe screen display format.

In the above embodiments, the tasks T1-Tn for carrying out displayprocessing are executed by the CPU 12, but may be executed by anotherCPU.

Also in the above embodiments, display areas have been defined inadvance, but the user may change the size and position of the displayareas.

Also in the above embodiments, each means in the general configurationis implemented by the CPU, but a part or all of the means may beconfigured by hardware logic.

10. Eighth Embodiment

10.1 General Configuration

In accordance with the above embodiments, it is judged whether thedisplay area subject to the acquisition requested can coexist with otherdisplay areas which have been used, and if coexistence is possible, useof the display area is allowed. However, processing units which areallowed use of the display area may be predetermined for each displayarea so that allowing use of the display area is judged according tothis information.

FIG. 45 shows the general configuration of the display control device 2according to the eighth embodiment. The display area storage means 6stores definitions of the display areas set on the screen of the displaydevice 8. In this embodiment, acquisition right information storagemeans 30 connected to the display area management means is disposed. Theacquisition right information storage means 30 stores processing unitswhich can be allowed use of the display area for each display area. Whenone of the tasks T1-Tn requests acquisition of a display area, thedisplay area management means 4 judges whether use of the display areacan be allowed to the task based on the content stored in theacquisition right information storage means 30. If the acquisition rightfor the requested display area is given to the task in the acquisitionright information storage means 30, use is allowed. If the acquisitionright is not given, use is not allowed.

10.2.1 Example when One Processing Unit is Allocated to One Display Area

The hardware configuration, when this embodiment is applied to digitalsatellite broadcasting, is shown in FIG. 3. FIG. 46 shows a display areadefinition example in accordance with this embodiment. FIG. 47 shows thedisplay area definition table stored in the ROM 16. And FIG. 48 showsthe acquisition right information table stored in the ROM 16. Accordingto this acquisition right information table, use of the display area E1is allowed to the task T1, use of the display area E2 is allowed to thetask T2, and use of the display area E3 is allowed to the task T3.

FIG. 49 shows a flow chart of the acquisition request processing portionof the display control program stored in the ROM 16. For example, thecase when the task T3 requests acquisition of the display area E1 willbe explained. At first, the CPU 12 obtains the acquisition rightinformation table from the ROM 16 (Step S901). Then the CPU 12 judgeswhether the task T3, which requested the acquisition, has an acquisitionright for the display area E1 referring to the acquisition rightinformation table (Step S902). In this case, the task T3 does not havean acquisition right for the display area E1, so the CPU 12 notifies anacquisition failure to the task T3 (Step S904).

When the task T1 requests acquisition of the display area E1, the CPU 12also judges whether use is allowed referring to the acquisition rightinformation table in the same manner (Step S902). In this case, the taskT1 has an acquisition right for the display area E1, so the CPU 12notifies an acquisition OK to the task T1 (Step S903).

In this way, in accordance with this embodiment, each display area isdefined so as not to overlap, and only one processing unit (task) isallowed use of each display area, therefore the display of each taskdoes not overlap and is not lost.

10.3 Example when a Plurality of Processing Units are Allocated to OneDisplay Area

The acquisition right information table may be defined as shown in FIG.50, so that one display area can be used by a plurality of tasks(processing units). In this state, acquisition request processing isexecuted so that only one task (processing unit) is allowed use of eachdisplay area. For example, when the task T1 requests acquisition of thedisplay area E1, use is allowed if no other tasks have acquired thedisplay area. When the task 1 requests acquisition of the display areaE1, use is not allowed when another task (task T2 or T5) has acquiredthe display area.

In this way, when a plurality of tasks (tasks which have an acquisitionright for the display area) request acquisition of one display area, thetask which requested acquisition first is allowed use of the displayarea. However, the task which requested acquisition last may be alloweduse of the display area. Also priority may be assigned to each task inadvance so that a task which has the highest priority is allowed use ofthe display area.

10.4.1 Example when a Plurality of Tasks are Allowed to Use One DisplayArea

In this example, when a plurality of tasks (tasks which have anacquisition right for the display area) request acquisition of onedisplay area, a plurality of tasks which requested acquisition areallowed use of the display area. In this case, display processing isexecuted by the plurality of tasks which are allowed use of the displayarea for the one display area. Therefore, in this case, displayprocessing among the plurality of tasks which are allowed use of the onedisplay area is adjusted among the tasks. In other words, an adjustmentof display processing among the tasks is necessary, but this adjustmentamong the tasks is easy since the number of tasks which can use eachdisplay area is limited.

The upper limit of the number of tasks (number of processing units)which can be used simultaneously may be defined in the acquisition rightinformation table, as shown in FIG. 51. In this table, use of thedisplay area E1 is allowed to the tasks T1, T2 and T5, but the number oftasks which can be allowed simultaneously is defined as 2. Use of thedisplay area E2 is allowed to the task T2, and the number of tasks whichcan be allowed simultaneously is defined as 1. Also, use of the displayarea E3 is allowed to the task T3 and T4, and the number of tasks whichcan be allowed simultaneously is defined as 2. In this embodiment, thework memory 14 has the acquisition status storage table shown in FIG.53, to manage the number of tasks using each display area.

FIG. 52 shows a flow chart of acquisition request processing inaccordance with this embodiment. Here, the case when the task T5requests acquisition of the display area E1 while the tasks T1 and T2have been allowed use of the display area E1, as shown in FIG. 53, willbe explained as an example.

At first, the CPU 12 obtains the acquisition right information (StepS1001), and judges whether the task T5 has an acquisition right for thedisplay area E1 (Step S1002). In this case, the task T5 has theacquisition right (see FIG. 51), so processing advances to Step S1003.In Step S1003, the CPU 12 obtains information on the number of tasksusing the display area E1 referring to the acquisition status storagetable in FIG. 53. In this case, the CPU 12 recognizes that two tasks, T1and T2, are using the display area E1.

Then the CPU 12 judges whether the number of tasks using the displayarea, which is 2, is smaller than the number of tasks which can use thedisplay area written in the acquisition right information table, whichis 2 (Step S1004). In this case, the former is not smaller than (equalto) the latter, so the CPU 12 judges that no more tasks are allowed useof the display area, and notifies an acquisition failure (Step S1007).

In this way, tasks exceeding the number of tasks which can use thedisplay area are not allowed use of the display area. By limiting thenumber of tasks which can use the display area like this, the adjustmentof display processing among tasks is prevented from becomingcomplicated.

In the above embodiment, the CPU 12 refers to the acquisition rightinformation table, as shown in FIG. 50, and the task T3 is not alloweduse of the display area E1, for example. However, a task which is notwritten in the acquisition right information table, such as the task T3,may be allowed use of the display area if acquisition is requested bythe task alone, so that when acquisition is requested by a task havingan acquisition right (e.g. T1), the task having the acquisition right isallowed use of the display area and use by the task T3 is cancelled.

The eighth embodiment can be implemented by combining with one of thefirst to seventh embodiments. Also for the eighth embodiment, amodification similar to the second to seventh embodiments can be appliedto the first embodiment.

While the embodiments of the present invention, as disclosed herein,constitute preferred forms, it is to be understood that each term wasused as illustrative and not restrictive, and can be changed within thescope of the claims without departing from the scope and spirit of theinvention.

1. A method for controlling a display on a display device, comprising:receiving requests from an application for acquiring one ofpredetermined display areas; rejecting the requests from applicationsexcept for a request from an application for acquiring the same one ofpredetermined display areas; storing the rejected requests; andproviding an authorization for acquiring the same one of predetermineddisplay areas to a single application whose request was stored in orderof a predefined propriety assigned to each application.
 2. A device thatcontrols a display on a display apparatus, comprising: a receiver thatreceives requests from an application to acquire one of predetermineddisplay areas; a rejecting device that rejects requests fromapplications except for a request from an application for acquiring asame one of predetermined display areas; a memory that stores therejected requests; and an authorization device that authorizes acquiringthe same one of predetermined display areas to a single applicationwhose request was stored in the memory in order of a predefinedpropriety assigned to each application.
 3. A computer readable mediumthat stores a plurality of instructions to be executed, the plurality ofinstructions comprising: receiving a request from the processing toacquire one of predefined display areas; determining whether to rejectrequests from applications except for a request from an application thatacquires the same one of predefined display areas; storing the rejectedrequests to a memory; and providing an authorization to acquire the sameone of the display areas to a single application whose request wasstored in the memory in order of a predefined propriety assigned to eachapplication.